A flash memory is a non-volatile memory like a hard disk, has fast access speed, and consumes less power, and thus it is widely used in a built-in system, a portable device, and the like.
To perform a writing operation upon a memory sector that has been already written, the flash memory must perform an operation of erasing the entire block including the corresponding sector in terms of its hardware characteristics. Partial programming, in which data is written to a part of pages that constitute a flash memory block, is possible.
A solid state drive is a device for storing information using a semiconductor and is abbreviated as “SDD”. The SSD operates in substantially the same manner as a hard disk drive (HDD). Since the SSD is compatible with ATA interface, it is easy to substitute the existing HDD with the SSD. Moreover, since the SDD has no portion that mechanically moves, it significantly reduces the problems associated with the SDD, such as long search time (seek time), latency, mechanical delay, and failure.
The SSD is also called a flash drive. The SSD based on flash memory does not require a battery and can be used as a substitute for 1.8, 2.5, and 3.5 inch HDDs. Since the SSD uses a non-volatile memory, data is not damaged even in the event of a sudden power failure. The flash memory is slower than DRAM but can operate at a higher speed than the currently used HDD.
FIG. 1 is a diagram showing a structure of an SSD, which comprises a plurality of flash memories 10 capable of storing data that a host 30 wants to write and a flash controller 20 that accesses the flash memory 10 to write or read data.
The flash controller 20 comprises a host interface 21 transmitting and receiving data to and from the host 30, a flash memory interface 23 transmitting and receiving data to and from the flash memory 10, and a microprocessor 22 managing a file system of the flash memory 10 and mapping a logical address to a physical address when data is written or read.
However, the SSD can write and erase data at all time. Thus, data may be easily erased even in the case where data is written to the SSD and released for distribution. Moreover, unlike the optical disk drive, the SSD has a problem that data should be transferred to the host and retained therein even in the case where data is to be stored.
A memory drive comprising a storage memory such as a hard disk (HD) or MRAM and a storage memory controller also can write and erase data at all time. Accordingly, the memory drive also has the problem that data can be easily erased even in the case where data is written to the memory drive for distribution.
Moreover, in the case of a memory drive that includes the SSD has a problem that cannot be used in an electronic device that uses an optical disk drive.